Nick Huggett

The two books discussed here make important contributions to our understanding of the role of spacetime concepts in physical theories and how that understanding has changed during the evolution of physics. Both emphasize what can be called a ‘dynamical’ account, according to which geometric structures should be understood in terms of their roles in the laws governing matter and force. I explore how the books contribute to such a project; while generally sympathetic, I offer criticisms of some historical claims concerning Newton, and argue that the dynamical account does not undercut ontological issues as the books claim.

We explicate recent results that shed light on the obscure and troubling problem of renormalization in Quantum Field Theory. We review how divergent predictions arise in perturbative QFT, and how they are renormalized into finite quantities. Commentators have worried that there is no foundation for renormalization, and hence that QFTs are not logically coherent. We dispute this by describing the physics behind liquid diffusion, in which exactly analogous divergences are found and renormalized. But now we are looking at a problem that is physically and formally well-defined, proving that the problems of renormalization, by themselves, cannot refute QFT.

The positivistic Received View construed scientific theories syntactically as axiomatic calculi where theoretical terms were given a partial semantic interpretation via correspondence rules connecting them to observation statements. This paper assesses what, with hindsight, seem the most important defects in the Received View; surveys the main proposed successor analyses to the Received View—various Semantic Conception versions and the Structuralist Analysis; evaluates how well they avoid those defects; examines what new problems they face and where the most promising require further development or leave unanswered questions; explores implications of recent work on models for understanding theories; and rebuts the few criticisms of the Semantic Conception that have surfaced.

Physical time plays a different role in general relativity than in quantum mechanics and the particle physics based on it. The first section of this chapter provides a brief survey of the main approaches to quantum gravity and then proceeds to consider the lessons that can be drawn from two distinct strategies for discovering a theory of quantum gravity. In the next section, the chapter first explicates the fate of time in approaches to quantum gravity that start with general relativity (GR) and attempt to quantize it. Second, it investigates approaches to quantum gravity that start from quantum particle physics. The third and fourth sections respectively offer an assessment of time as understood in string theory and 'non‐commutative' field theory. One of the important possibilities for time in quantum gravity is that it might fail to commute with space.

Learning through original texts can be a powerful heuristic tool. This book collects a dozen classic readings that are generally accepted as the most significant contributions to the philosophy of space. The readings have been selected both on the basis of their relevance to recent debates on the nature of space and on the extent to which they carry premonitions of contemporary physics. In his detailed commentaries, Nick Huggett weaves together the readings and links them to our modern understanding of the subject. Together the readings indicate the general historical development of the concept of space, and in his commentaries Huggett explains their logical relations. He also uses our contemporary understanding of space to help clarify the key ideas of the texts. One goal is to prepare the reader (both scientist and nonscientist) to learn and understand relativity theory, the basis of our current understanding of space. The readings are by Zeno, Plato, Aristotle, Euclid, Descartes, Newton, Leibniz, Clarke, Berkeley, Kant, Mach, Poincaré, and Einstein.

This work first explicates the philosophy of classical and quantum fields and particles. I am interested in determining how science can have a metaphysical dimension, and then with the claim that the quantum revolution has an important metaphysical component. I argue that the metaphysical implications of a theory are properties of its models, as classical mechanics determines properties of atomic diversity and temporal continuity with its representations of distinct, continuous trajectories. ;It is often suggested that classical statistical physics requires that many particle states be represented so that permuting properties leads to distinct states; this implies that individuals can be reidentified across possible worlds in a non-qualitative way. I show there is no evidence for this conclusion, an important result, for it is claimed that quantum particles are not individuals. This claim is based on the misconception about classical statistics, but also on a conflation of notions of identity; I show that, while transworld identity is incompatible with quantum mechanics, other classical notions may be consistently ascribed. I also give a field-particle distinction that applies usefully in both quantum and classical domains. In the former the distinction helps defeat claims of underdetermined by data, in the latter it helps provide a minimal field metaphysics. ;Next I tackle renormalisation: I show how divergences occur in approximate, perturbative calculations, and demonstrate how finite, empirically verified, answers are obtained. These techniques seem to show that the predictions are not logical consequences of the exact theory. I use the techniques of the renormalisation group to establish that perturbative renormalised quantum field theory does indeed approximate the consequences of field theory. ;Finally, I discuss the idea that renormalisation proves that there can be no quantum theory of everything, only a patchwork of effective theories. The preceding chapter shows that renormalisation demonstrates only that the picture is consistent, and this is insufficient to show that physics must be phenomenological